The present invention relates to methods of electrodeposition, particularly anodic electrodeposition.
Manufacturers of industrial products such as metal furniture, appliances and other small to moderate sized metal parts to a large extent consider electrodeposition the method of choice at least for priming the metal part and in many instances also for topcoating to produce the finished product. Such manufacturers have come under increased pressure in recent years to minimize organic solvent emissions in their manufacturing process, in most instances a maximum limit being placed on total emissions for the entire coating operation. Since electrodeposition often is only one aspect of the coating operation which will liberate volatile solvents, it has become critical to achieve minimal to no solvent emissions in each aspect of the coating operation, in particular the electrodeposition process.
Typically, volatile organic solvents are introduced in the electrodeposition process from solvents used to formulate the aqueous electrocoating composition. These are often introduced during preparation of pigment grind compositions which are used to incorporate a pigment component into the electrocoating composition. Generally, a pigment grind composition is prepared by blending pigment, dispersing agent or grind vehicle and other optional additives together with organic solvent into a paste which is then blended with a major portion of the film forming vehicle to produce the final coating composition. Depending upon the pigment and grind vehicle, excessive amounts of organic solvent may be required to incorporate and adequately disperse the pigment.
There is a need, therefore, for a method of electrodeposition which has minimal volatile organic content introduced with the pigment grind composition.